Safety mechanism for electrically detonated projectiles



April 25, 1961 J. c. KOPEC 2,981,191

SAFETY MECHANISM FOR ELECTRICALLY DETONATED PROJECTILES Filed Aug. 6, 1956 5 Sheets-Sheet 1 Fig.1

John GKopec INVENTOR.

J. C. KOPEC Apr 5 Sheets-Sheet 2 ELECTRON/C FIR/N6 CONTROL HEAD ENERG/ZER John GICqpec INVENTOR.

BY &

T'TORNEY' April 25, 1961 J, c, o Ec 2,981,191

SAFETY MECHANISM FOR ELECTRICALLY DETONATED PROJE CTILES Filed Aug. 6, 1956 5 Sheets-Sheet 3 Fi g3 John C. Kgvec INVENTOR.

J. C. KOPEC April 25, 1961 SAFETY MECHANISM FOR ELECTRICALLY DETONATED PROJECTILES Filed Aug. 6, 1956 5 Sheets-Sheet 4 John CfKo oec INVENTOR.

BY XE. Z- M W0 A TORNgYS' April 25, 1961 J. c. KOPEC 2,981,191

SAFETY MECHANISM FOR ELECTRICALLY DETONATED PROJECTILES Filed Aug. 6. 1956 5 Sheets-Sheet 5 JohnaKo oec r 7 INVENTOR.

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2,981,191 1 Patented Apr. 25, 1961 SAFETY MECHANISM FOR ELECTRECALLY DETONATED PROJECTILES John C. Kopec, Rochester, N.Y., assignor, by mesne assignments, to the United States of America as represeated-by the Secretary of the Navy Filed Aug. 6, 195-6, Ser. No. 602,476

2 Claims. (or. 102-701 This invention relates to ordnance projectiles ofv the electrically detonated type and is particularly concerned with safety mechanism to prevent accidental detonation of the projectile, while still insuring properoperation upon firing.

In ordnance projectiles of the type equipped with the so-called proximity fuse it is desirable that the electronic firing mechanism carried by the projectile be maintained in an unarmed or inactive condition until a predetermined time has elapsed after firing of the projectile. It is furthermore desirable that this time delay be readily adjustable but in no event should the detonating mechanism be rendered operative until after the elapse of a predetermined minimum time after firing, thus insuring that the projectile will be safely away from the firing position before it becomes armed. It is likewise essential that the mechanism which provides this adjustable arming, delay be relatively simple and lightweight and so constructed that accidental arming during transportation or handling of the projectile will be efiectively prevented.

It is an object of this invention toprovide a safety mechanism for such a projectile which will satisfy the above requirements and which, at the same time, is readily adaptable to mass production techniques.

A further object is to provide in such a projectile centrifugally controlled electric switch means which, prior to firing of the projectile, form a primary short circuit directly across the electrical detonator and a secondary short circuit directly across the output of the electronic firing head, and which at the same time, open the electrical connections between the power source or energizer and the firing control head as Well as between the firing control head and the detonator. I

It is a further object to provide such a safety mechanism wherein the primary short circuit will be brokenonly after a predetermined minimum lapse oftime after firing and wherein the secondary short circuit and operative connections from the electronic firing control head to the power source will be completed only at the end of an adjustably present time interval after firing.

Further objects will become apparent from the following description and claims especially when considered in the light of the accompanying drawing wherein:

Fig. 1 is a fragmentary longitudinal section through a projectile incorporating the invention.

Fig. 2 is a diagrammatic View of the electrical control Fig. 3 is afront view of the clock mechanism anduprimary shorting switch utilized in the projectile, parts being broken away to better show the arrangement of certain elements.

'Fig. 4 is a fragmentary longitudinal section taken generally on the line 44 of Fig. 3.

Fig. 5 is a'transverse section taken substantially in the plane indicated by the line 55 in Fig. 1.

Fig. dis a transverse section view showing the arrangement of the timing disk assembly used for actuating certain of the switches.

Figures 7 and 8 are sectional views taken on the lines 77 and 88 respectively of Fig. 6.

Fig. 9 is a fragmentary side view of a portion of the timing disk assembly with parts broken away to show the interior.

A portion of an ordnance projectile is shown in Fig. 1 I

and comprises a main casing 1 having a sleeve 2 threadedly engaged in the forward end thereof. A nose membar 3 is carried by sleeve 2 for relative rotational adjustment about the longitudinal axis 4 of the projectile, this adjustment, as will later be clear, being for the purpose of setting the arming delay time. As illustrated, the nose 3 is retained in the forward end of the sleeve 2. by means of a suitable wire spring 5 seated in opposing grooves 6 and 7 in the nose and sleeve respectively. The arrangement is such that the nose can be inserted into the sleeve by forcing it past thespring 5 until the latter snaps into the groove 6. A plurality of set screws 7' one of which is shown in Fig. 1, are provided for engaging the spring. 5 to securely hold the nose in place.

Carried by and within the nose 3 is a conventional fuse of the proximity type including an electronic firing control head 8 and a power source or energizer 9 rigidly secured together andto the nose 3 so that they are rotatably adjustable about the axis 4 with the nose 3. As illustrated in Fig. 1 the members 8 and'9 are provided with a flange 10 about which the rear edge of the nose 3 is formed to securely clamp these elements together.

Rigidly secured to the rear end of the housing 11 of the energizer 9 is a switch ring assembly 12 arranged to coact with a timing disk assembly 13 rigidly carried by the timing shaft 29 of a conventional timing clock mechanism 14 (see Fig. 2). The clock mechanism 14 is rigidly carried by the sleeve 2, being held in position by means of a ring member 15 threaded into the rear end of the sleeve 2.. To prevent relative rotation of the. clock 14 and the sleeve 2, the wall 16 of the latter is depressed inwardly as at 17 into mating engagement with a groove 18 formed in the outer periphery of the clock mechanism. With this arrangement the clock mechanism 14 will be maintained in fixed relationship to the main casing 1 of the projectile while the switch ring assembly 12 maybe adjustably positioned relative thereto about the axis 4 by rotating the nose 3 into the desired relationship. Timing disk 1'3, which carries certain switch actuating elements to be later described, rotates .with the timing shaft 29 of the clock mechanism 14 and therefore will determine the time after firing when the switch mechanisms in the switch ring 12 will be actuated. As shown in Fig. 1 the forward end of the clock mechanism carries a commutator ring 19, insulated therefrom, and against which bears a contact finger 20 carried by the switch ring -12. As will later appear, this commutator and con tact finger serve as part of the electrical connection from the firingcontrol head to the detonator 22.

Turning now to Fig. 2, the electrical switching arrangement is diagrammatically illustrated and a consideration of this figure will assist in an understanding of the detailed description to follow. A primary switching mechanism 21, carried by and controlled by the clock mechanism 14 serves, in the pre-firing condition, to form a primary short circuit directly across the electrical detonator' 22 and, after firing of the projectile to open this short circuit and complete a connection from the commutator ring 19 to the detonator. Carried by the switch ring 12 is a secugallyresponsive pellet 24' normally carried within the timing disk 13. -Also carried by'the switch ringlz is a second switch mechanism 25 inserted between one side of the energizer and the main body of the projectile itself, which is diagrammatically shown in this figure as being a ground connection. This switch 25 is adapted to be closed by a pellet 26 which is .also normally housed within the timing disk 13. The time, after firing, at which.

and, as soon'as the plunger 34 engages the contact 43 a connection will be made from the detonator through the -sleeve32', plunger 34 and contact 43 to the commutator ring 19. Switch mechanism 21 therefore constitutes, in effect, a single polo double throw centrifugally' actuated switch.

The switch ring assembly 12,- which carries-switch I i means 23 and 25, is best shown in Figs. 1 and and comto the lower portion of the energizer casing 11.

secondary shorting switch 23 comprises a member 43 pivotallymounted on a pin 49 and arranged so that its Figs. 3 and 4.- As shown in Fig. 4 the forward end of -theclo'ck mechanism 14 carries a block 27 having-a hollow interior 28 through which the clock shaft 29 extends. Rigidly carried: by the shaft 29 within the chamber 28 is "a bifurcated'arm 30 which, as-will laterbe explained; controls the primary switching mechanism. 1 'No' details of theclock mechanism itself are shown sincesuch clock mechanisms are well known in the art.

prises a disk. 46 ofinsulating material carried within a shallow metal casing 47 which is in turn securely fastened The outer end 50 will normally contact a second pin 51. Pin 51 is electrically connected to a generally arcuate I contact strap 52 carried by the rear face of the insulating disk .46, a portion of this strap being bent rearwardly to form the contact finger 20. As illustrated in Fig. 2

the pin 51 is also connected by lead 52" to the output of the electronic firing control head 81 The pivot pin v49 is 1 connected directly to the energizer casing and is therefore Suifice it-to say that the clock shaft 29 during operation rotates,- at a predeterminedrate under the control of a suitable escapementmechanism, in a clockwise direction as {viewed in Fig. 3. 'The'fully wound position being iudicated'by the solid line position of the arm and the'unwound position being shown by the dotted lines 31.

As is usual with such timing mechanisms used in ordnance I projectiles, the'clock' mechanism will of course be provided with the usual set back mechanism which will maintain the clock inoperative. until actual firing of the projectile. the clock mechanism will'be arranged with a centrifugally I actuated control member to insure that the clock cannot 'Also, in accordance with the usual practice,

run'until the projectile is rotating at a relatively high speed. 5 Neither of these safety devices are illustrated since,as previously stated, they are common and well known in the art. I

Extending radially through is insulated from the plug 27' by means of insulating material 33. Axially slidable within this sleeve is a metal plunger 34 provided at its inner end with a flange 35. As best illustrated in Fig. 3 this flange 35 is adapted to pass between the opposed tips 36 and 37 of the bifurcated arm 30 and, in the fully wound position of the clock, to be engaged by the tip member 36 so as to restrain the plunger 34 against radial outward movement.

The outer end of the sleeve 32 is provided with an integral tab 38 to which is connected the lead 39 from the detonator 22 (see Figs. 1 and 2). The other lead 40 from the detonator is connected directly to the clock mechanism, which, as previously explained is considered as ground so that in the pre-firing condition of the projectile there is a direct electrical short circuit across the detonator through the clock mechanism 14, its shaft 29, arm 30, plunger 34 and sleeve 32.

The previously mentioned commutator ring 19 is carried on the forward face of block 27 by means of insulating rings 41 and 42. As best shown in Figs. 1 and 4 commutator 19 includes a rearwardly extending contact element 43 which extends opposite the outer end of sleeve 32 and which, when the plunger 34 is in its retracted position, is spaced radially outwardly from the outer end 44 thereof. As illustrated in Figs. 1, 3 and 4, a suitable insulating cover 45 is provided for these elements.

With this arrangement, as soon as the clock shaft 29 has rotated slightly in a clockwise direction from its Fig. 3 position, the flange 35 of plunger 34 will be released by the tip member 36 and will fly radially outwardly into contact with the commutator contact 43 under the action of the centrifugal force arising from the rotation of the projectile. As soon as the flange 35 leaves the member 36 the short circuit across the detonator 22 will be br oken the block 27 and into the i interior chamber 23 thereof is a metallic sleeve 32which effectively grounded. Switch element 48 .is mounted within a recess 53 formed in the insulating disk-46, this i recess'being provided with a mouth 54 facing the timing v 25 disk 13 for the passage of pellet 24. When, as will later be explainedin detail, the pellet 24 isreleased from the timing disk 13 will pass through the mouth 54 and into engagement with the end. 54'of'lever .48 so that the centrifugalforce acting thereon will be sufiicient to rotate 7 member 48 about pin 49 and out of contact with the pin 51 so as to remove the short circuit across the output y of the electronic firing control head.

Also extending into a suitable recess 55 formed in th rear surface of insulator .46 area pair of contact pins 56 and 57. As best illustrated in Fig. 2 pin 56 is connected to one side of the energizer 9 while pin 57. is directly 1 grounded to the casing 11. .When. upon rotation, of

timing disk 13 into the proper position, pellet 26 is released therefrom, it will move by centrifugal force into the recess 55 bridging the pins '56 and S7 and completing the ground return circuit between the energizer 9 and the electronic firing control head 8.

The timing disk assembly 13 is best shown in Figs. 6 through 9 and comprises a hub 59 adapted to be rigidly afiixed to the forward end of clock shaft 29 and which in turn rigidly carries a cylindrical casing 60.. Carried upon hub 59 within the casing 60 are three plate members 61, 62 and 63, plates 61 and 63 being fixed against rotation relative to the hub and casings 60, whereas plate 62 is mounted for limited rotation thereabout against the action of a spring 64. A suitable cover plate 65 covers the forward end of the timing disk assembly.

As shown in Figs. 6 and 7 pellet 24, which serves to actuate secondary shorting switch 23, is loosely confined between the fixed plate 61 and the cover plate 65. Generally opposite pellet 24 the wall of casing is provided with an opening 66 of suflicient size to permit the passage of pellet 24outwardly from the casing. Prior to firing of the projectile, pellet 24 is restrained against outward movement by coacting flanges 67 and 68 which extend forwardly respectively from plates 62 and 61. However, upon firing of the projectile the centrifugal force acting on pellet 24 will cause it to apply a force against flange 67 of plate 62, tending to cause the latter to rotate in a clockwise direction as viewed in Fig. 6 to an extent sufiicient for the pellet to be free to escape through the opening 66. However, as will be clear from Fig. 5, actual escape of pellet 24 from the assembly 13 cannot take place until the opening 66 in the timing disk has been moved by the timing clock 14 into a position opposite the mouth 54 of recess 53.

Pellet 26 which controls switch 25 is similarly loosely confined within the casing 60 between the forward plate 63 and the rear wall thereof. As best shown in Figs. 6 and 8 the stationary front plate 63 is provided with a rearwardly extending flange 71 and the center plate 62 is provided with a rearwardly extending flan'ge 70' which normally prevent pellet 26 from moving outwardly through the adjacent opening 69 in the casing wall. Like pellet 24, upon rotation of the shell or projectile after firing, centrifugal force acting upon pellet 26 reacts against the flange 70 to tend to turn the plate 62 in the clockwise direction as viewed in Fig. 6 so that this pellet will be free to escape through the opening 69 and, when the latter has been brought opposite the recess 55 in the switch ring 12, to fly outwardly into a position bridging the contact pins 56 and 57-. It should be noted that, while actions of pellets 24and 26 have been separately described, both will be acted upon by centrifugal force at the same time, and they therefore act conjointly to produce the described clockwise rotation of plate 62 against the restraining action of spring 64.

In order to insure that plate 62 will not be allowed to rotate until after actual firing of the projectile, a set back arrangement is provided. As best shown in Figs. 6 and 9 the rearmost plate 61 is provided with a pair of slots 72 and 73 extending completely therethrough, slot 72 extending to the peripheral edge of this plate 61 to form a tongue 74 as an integral part of the plate 61. The metal at the ends of the slot 73 is machined or coined so as to form a pair of relatively weak necks 75 and 76 connecting'the tongue 74 to the remainder of the plate 61. Near the outer end of the tongue 74 a portion thereof is bent forwardly so that it forms a flange 77 which extends into and somewhat beyond the plane of plate 62, plate 62 being provided with a notch 78 for the reception of this flange. So long as the flange 77 extends into the notch 78 plate 62 will be effectively held against rotation so that the pellets 24 and 26 cannot escape from the timing disk assembly. However, at the time of firing of the projectile, the, acceleration forces will be sufficiently high that the tongue 74 will, due to its own inertia, bend rearwardly about the necked portions 75 and 76 into the dotted line position shown at 79 in Fig. 9. Therefore the flange 77 will be moved rearwardly out of the plane of the plate 62, thereby freeing the latter for rotation relative thereto.

The operation of the device is believed to have been made clear from the previous description but will now be summarized. Clock 14 will be wound to its fully wound position and plunger 34 will be engaged with the bifurcated end of arm 30 on the clock shaft 29 at the time that the projectile is made ready for firing. This will be done prior to assembly of the nose and fuse with the projectile itself, an opening 45' in the forward face of block 27 of the clock assembly providing access to the inner end of the plunger 34 to facilitate the engagement thereof with the tip 36 of the arm 30. As previously de scribed this also establishes the primary short circuit across the detonator 22. After assembly of the timing disk 13 on the forwardly protruding end of clock shaft 29, the nose assembly 3 which, as previously described, carries the electric firing control head 8, the energizer 9, and the switch ring assembly 12, will be snapped into place and set screws 7' tightened. Prior to firing, the nose assembly 3 will be rotatably adjusted about axis 4, into a position to set the desired arming delay period, suitable calibration marks (not shown) being provided on the nose 3 and sleeve 2 to facilitate this setting. The friction afiorded by the joint between the nose 3 and sleeve 2 is sufficient to maintain the parts in adjusted position relative to one another. Fig. 5 is illustrative of the relative positions of the timing disk 13 with its pellets 24 and 26 and the switch ring assembly 12 after such adjustment. 1

Upon firing of the projectile the acceleration forces involved will, as previously described, actuate the usual set back safety mechanism conventionally built into the clock mechanism 14 and will also cause the locking flange 74 of the plate 61 in the timing disk assembly to bend rearwardly to freethe plate 62 for rotation. Moreover, as is common with such projectiles, the projectile will, as soon as it has been fired, begin to spin rapidly about its longitudinal axis, the resulting centrifugal force freeing the clock mechanism for operation and, at the same time, urging pellets 24 and 26 to move radially outwardly through the openings 66 and 69 and into contact with the inner peripheral wall of the switch ring 12. The clock mechanism will thereupon begin to operate, slowly rotating shaft 29 at a predetermined rate in the clockwise direction and, after a relatively small amount of rotation, the plunger 34 of the primary switching mechanism 21 will 'be free from engagement with the tip 36 of arm 30 and will fly outwardly to break the primary short circuit across the detonator and complete the electrical connection from the firing control head to the detonator. However, complete arming of the fuse will not occur until the clock has run sufiiciently long to rotate the timing disk 13 into position wherein openings 66 and 59 are opposite the corresponding recesses 54 and 55 in the switch ring. During this time the short circuit will be maintained across the output of the electronic firing control head by the member 48 of secondary shorting switch 23.

As shown in Fig. 5 the mass of that portion of member 43 to the left of pivot pin 49 is somewhat greater than that of the portion to the right of this pivot so that the centrifugal force will tend to urge the tip 50 thereof into firm contact with the pin 51. However, as soon as the timing disk has been rotated relative to the switch ring 12 'sufiiciently 'to align opening 69 with recess 55, pellet 26 will fly into the recess 55 so as to bridge the pins 56 and 57,.tl1'ereby completing the ground circuit between the energizer and firing control head. Shortly thereafter opening 66 will align itself with the mouth '54 of recess 53 and pellet 24 will fiy outwardly int-o recess 53 so as to engage the free end of switch'member 48 with suificient force to break the contact between pin 51 and tip 50, thus removing the secondary short circuit. The fuse will therefore now be fully armed and, will be under the control of the electronic firing control head 8. Upon approach of the projectile to its target, the electronic control head, will, as is well known in the art, generate an output pulse which will be applied to the detonator 22 by Way of the pin 51, contact finger 20, commutator ring 19, tab 43, plunger 34, sleeve 32, and lead 39, causing detonation of the detonator 22 and thereby initiating explosion of the projectile.

Thus, it can be seen that a fuse assembly embodying my invention is substantially fool-proof prior to actual firing but, at the same time, will become fullyarmed at the desired time after firing. Both a combination of high acceleration forces and a relatively high speed rotation are required to render the safety switch mechanism operative to arm the fuse so thatthe fuse will remain relatively safe despite abnormally rough handling. Yet the improved safety mechanism of my invention involves but relatively few, easily manufactured and assembled components which are readily adaptable to mass production techniques.

While but one embodiment of the invention has been shown and described in detail, it is obvious that many variations and modifications can be made without departing from the scope and spirit of the invention.

I claim:

1. Safety mechanism for an electrically detonated I ordnance projectile having an electrically ignited detonism including a timing shaft electrically connected to said body member and rotatable from a predetermined initial position in response to operation of said clock mechanism, a primary safety switch mechanism carried by said first member and comprising a conductive sleeve extending, generally radially of said axis and spaced outwardly'therefrom, said sleeve being insulated from said first member, a switch contact insulated from said first member and said sleeve and mounted opposite the outer end of said sleeve, means for establishing electrical connections from one side of said pulse generating means to said contact and from the other side thereof to said body members, electrical connections from one side of said detonator to said conductive sleeve and from the other side thereof to said clock shaft, a conductive plug slidable in said sleeve between inwardly retracted position spaced from said contact and an outwardly active position engaging said contact, a conductive arm carried by said shaft adapted, when said shaft is in said initial position, to engage said plug and retain it in said retracted position whereby said sleeve, plug and arm establish a primary short circuit across said detonator, said arm being adapted upon a predetermined movement of said shaft from said initial position to disengage said plug whereupon the latter will be free to move by centrifugal action into engagement with said contact to complete the electrical connection from said pulse generating means to said detonator, a normally closed switch carried by said second body member, having one terminal insulated from said body member and electrically connected to said one side of said pulse generating means and the other terminal being electrically connected to said second body member whereby to normally form a secondary short circuit directly across the output of said pulse generating means, switch actuating means carried by said shaft, means rendering said actuating means inoperative until said shaft has rotated into a predetermined relationship relative to said switch, said actuating means thereupon being responsive to centrifugal force to cause, opening of said switch.

2. Safety mechanism for an electrically detonated ordnance projectile having an electrically ignited detonator and electrical pulse generating means for causing ignition of saidjdetonator, said projectile including first and second body members selectively adjustable relative to one another about the axis of said projectile, electrical connections from said pulse generating means to said detonator including a single pole, double throw switch having a centrifugal force responsive actuating means therefor carried by said first body'member, a normally closed single pole, single throw switch carried by said second body member, providing, when closed, a short circuit across the output of said pulse generating means, a clock mechanism carried by said first body member adapted to be rendered operative upon firing of said projectile, said clock having a shaft rotatable from a predetermined initial position in response to operation of said clock mechanism, means carried by said shaft for maintaining said switch actuating means in one extreme position wherein said first mentioned switch provides a short circuit across said detonator and elfective upon a predetermined movement of said shaft relative to said first body member to release said actuating means whereby to render it responsive to centrifugal force to open said first mentioned short circuit and to connect said detonator to said pulse generating means, and other centrifugal-force responsive means carried by said shaft and rendered effective upon rotation of said shaft into a predetermined relationship relative to said second body member for opening said second mentioned switch.

References Cited in the file of this patent UNITED STATES PATENTS 2,682,223 Lewis June 29, 1954 

